M. O. Aboelfotoh and J. A. Lorenzen, "Influence of Secondary-Electron Emission from MgO Surfaces on Voltage-Breakdown Curves in Penning Mixtures for Insulated-Electrode Discharges," J. Appl. Phys., Vol. 48, No. 11, 4754-4759 (1977) discloses the formation of a MgO film on the surface of an a-c plasma display panel by sputtering, which involves use of an electron gun to volatilize a magnesium compound and then deposit it as a MgO film on the surface of the panel to a thickness of about 3000 A. The disadvantage of this method of forming the MgO film is that sputtering is expensive.